Magnetic flux generators, which may be transmitters wherein magnetoresistors or "Hall generators" are utilized as active elements, have an advantage compared to inductance transmitters, in that relatively low rpms or movements in the stoppage range may be acquired.
In the prior art, the magnetic flux transmitters, in particular bar-shaped transmitters, with a Hall generator arranged on the end face of a permanent magnet, supply a signal, which is relatively high in comparison with the obtained useful signal and which, because of the wiring pattern of the Hall generator, is temperature-dependent. This signal is further amplified during subsequent processing of the signal which is a significant drawback from measuring technology point of view.
A magnetic flux transmitter has become known from the DE-B 36 38 622, which improves the technical premises of such a bar-shaped magnetic flux transmitter, and especially, however, it supplies as high a useful signal to interference signal ratio as possible. This magnetic flux transmitter utilizes an annular magnet or a sleeve-shaped magnet as a permanent magnet, the aperture of which is allocated or positioned in such a manner, with respect to the Hall generator, that the axis of inductance of the Hall generator and the axis of the annular magnet essentially coincide with one another and further, that the Hall generator, with the magnetic circuit open, is disposed in a space of minimum magnetic inductance which is formed within the annular magnet through field displacement. Herein, there emerges the advantage, that due to the so-called ohmic zero component of the Hall generator, interference voltage levels, which result from manufacturing tolerances, may be compensated for by magnetically biasing the Hall generator. In this regard, the Hall generator is disposed to be offset with respect to the zone of minimum magnetic inductance.
This zero point compensation constitutes an extraordinarily sensitive positional adjustment between the permanent magnet and the Hall generator, which would cause considerable difficulties in mass production. The solution described in the DE B 36 38 622, wherein a finger-shaped extension is configured in such a manner, at the printed circuit board, that it is introducible into the aperture of the permanent magnet and that the Hall generator is attached at the end side of the printed circuit board extension, for various reasons is unsuitable for mass production. In particular, because of the coarse tolerances, which have to be accepted in the manufacture of the printed circuit board, and because of the considerable shape deviation of such permanent magnets which also have to be tolerated, an unjustifiably expensive mounting for the adjustment and the positional fixation for the subsequent solid connection of the permanent magnet, with the printed circuit board extension, becomes necessary.